Estimating expenses in rural northern Illinois

I am familiar with the 50% rule of thumb for estimating expenses, but am trying to analyze a duplex in rural northern Illinois and am trying to estimate expenses.  Can anybody provide feedback on the assumptions.  Too high?  Too low? Is plowing a necessary expense for a small driveway?  At what point is plowing necessary, if I look at other multi-families (6 units?)  Thank you in advance!

Estimated Expenses (annual)

Real Estate Taxes (estimated 4% purchase price)

Property Insurance (estimate 0.75% purchase price)

Property Management (11% rental income) 

Repairs & Maintenance (10% rental income) 

Utilities ($75 water / month / unit + $25 trash)

Lawn care (estimated $100 / month x 6 months)

Snow plow small driveway / parking  (estimate $100 / month x 3 months) 

Capital expenditures (10% potential rental income)